Skin lightening cosmetics are used by millions of individuals for lightening their natural skin color for cosmetic reasons and the number of such users is on the rise. However, the use of skin lightening cosmetics varies considerably among cultures. A major cosmetic concern among Indian and other Asian populations is the appearance of dark circles (melasma) around the eye region. This occurs due to a site-specific increased melanin production called hyperpigmentation. Melanin is the pigment or coloring agent of skin and is produced in melanocytes which are the pigment forming cells found in the basal layers of the epidermis. Many cosmetic products have been reported to control the amount of melanin production in hyperpigmented skin. The majority of these products act by inhibiting the tyrosinase enzyme, which is the only essential enzyme needed in the production of melanin. A number of tyrosinase inhibitors are used in cosmetic compositions. Hydroquinone is one of the first tyrosinase inhibitors used in skin lightening. However, the prolonged topical use of this compound has been associated with a variety of disorders, including infectious dermatosis, contact eczema, extended dermatophytosis, ochronosis, periorbitary dyschromia, and necrotizing cellulites (Raynaud E. et al., Ann Dermatol Venereol 128(6-7):720-724, 2001). Hydroquinone has also shown genotoxic and mutagenic activities (Jagetia G. C. et al, Toxicol Lett 121(1): 15-20, 2001). Reports of toxicity have led to banning of hydroquinone in Europe for use as a depigmenting agent and in the United States also its use is limited to solutions of 2% or lower concentration (Journal of the European Academy of Dermatology and Venereology; Volume 20 Page 777—August 2006; Skin Therapy Letter Volume 9 Number 6, June-July 2004). Hydroquinone has also been used in combination with other compounds such as Kojic acid (U.S. Pat. No. 5,279,834). However, it has been reported that such compositions provide only temporary effect and hyperpigmentation returns if use of the composition is discontinued.
Compositions containing other tyrosinase inhibitors namely bearberry, arbutin, rutin and ascorbic acid either alone or in combination with other pharmaceutically acceptable agents have been reported in the art (U.S. Pat. No. 4,818,768, U.S. Pat. No. 5,980,904, U.S. Pat. No. 5,747,006, U.S. Pat. No. 6,123,959, U.S. Pat. No. 5,882,658, U.S. Pat. No. 6,077,503 and U.S. Pat. No. 6,641,845; Japanese Published Patent Applications: JP 10-279421, JP 10-279422; PCT Published Patent Applications WO 02/055047 and WO 06/090939).
Cosmetic compositions such as those described above seem to have a moderate improved effect in lightening or whitening the skin. However, many of the compositions are either only marginally effective or provide only temporary lightening effect. Accordingly, there still exists a need to develop an improved skin composition for topical application, having the desired degree of effectivity, when applied to affected areas of skin. The present invention fulfills this need and provides further related advantages.